Try the G first, you might be surprised at the performance.
I recently got a freebie Linksys BEFW11S4 which is only 802.11b to use in my
shop, 100' from the house. I put it on the overhead shelf of my PC desk, so
it's about 15' from there to a window facing the shop; I use my wireless
laptop anywhere in the shop with no problem.

>I have a workshop that is 300 feet from my house.. I want to set up a
> computer in it and access the same wireless signal that is currently
> in my house.. Currently I have a wireless G router and I am wondering
> whether I should switch to the newer wireless N system or whether I
> should stick with wireless G and try to make directional antennas out
> of cans (as described on the internet).. (I haven't read about
> anybody making "homemade" directional antennas that work with the
> Wireless N system so I assume that the complexity (of 3 antennas)
> involved is too great).. My question is whether the wireless N signal
> can extend to 300 feet.. there is a clear "line of sight" between the
> two buildings ... My other question is whether I might be better off
> trying to run a cable between the two buildings.. I have plenty of
> two wire electrical cable (which I presume is not the right stuff) and
> also have 6 wire telephone cable. (I don't like the thought of
> leaving it lying on the ground so might want to bury it 6" or so)..
> Does anyone have any thoughts as to how I can best approach this
> situation..